The ability of a suspension system to absorb the shock imposed on the wheels of the vehicle in encountering terrain or road features is largely dependent on the extent of travel through which the wheels may move relative to the vehicle frame. While there are many considerations involved in the design of suspension systems for various type vehicles, for overall best performance, for military off-the-road vehicles, this factor is of most significance. That is, the maximum speed of the vehicle in negotiating cross country terrain features and the severity of the terrain roughness is limited by the extent of travel available from the suspension system. This is of course the measure of the suspension system's ability to absorb the impulse imposed on the wheel over an extended time period to thereby reduce the maximum force ultimately transmitted to the vehicle frame.
The resulting shock levels which cannot be tolerated are those which would preclude the driver maintaining effective control of the vehicle or would result in failure of vehicle components due to excessive stress levels. This design constraint is rendered more difficult by the military requirement that the suspension components by simple, rugged and reliable and shielded so as to be afforded maximum protection from damage from enemy fire or road obstructions. This, while still being reasonably accessible for maintenance functions on these components.
For track laying vehicles such as tanks, a trailing arm suspension combination with torsion bars adequately serves this goal. Wheeled vehicles, however, generally do not have sufficient chassis or hull width to enable adequate wind up of the torsion bar for maximum travel of the suspension system, and in addition, the torsion bar suspension does not readily lend itself to axially aligned wheel sets, which arrangement, of course, is required in wheeled vehicles.
Another constraint imposed is that of accommodating the suspension components within the vehicle hull if the vehicle is armored. If coil springs are utilized in the conventional manner, the height of the coil springs required to provide optimum travel would require a spring height which would either result in exposure of the springs outside the vehicle hull, or if enclosed would exceed the vertical depth of the vehicle hull available if extended travel were required.
Particularly is this so for front wheel suspension systems which are generally located in a region which requires sloping of the upper surfaces as a strong design objective. This necessarily requires a minimum hull dimension in this area. Leaf springs, on the other hand, generally cannot afford sufficient travel for a high performance suspension.
While adequate travel has been afforded provided by independent suspension systems, that is, systems in which each of the front wheels are supported independently of each other by the suspension system, the requirement that the wheels be supported so as to be capable of steering movement creates considerable complexity, particularly when the military requirements for simplicity and ruggedness are considered. Such vehicles usually also involve powering of the front wheels, and a drive to the wheels must be provided.
For this reason, there has not heretofore been provided an adequate front suspension system which provides for extended travel of the wheels by a simple rugged suspension system which is adaptable to hull configurations of minimal depth and which allows relatively easy access to the components thereof requiring maintenance.
An additional complicating feature in such suspension systems is the requirement for shock absorbers to provide a dampening or dissipating force on the suspension movements. A shock absorber of conventional piston-in-cylinder design is an item of considerable vulnerability and complexity and a major maintenance item.
While the rear suspension design is not as difficult since it is not required to be adapted to steering and not located in a region of narrow hull width, it nonetheless should accommodate the same travel as the front suspension.
Such military vehicles are often required to negotiate vertical obstacles of considerable height. The ability of the vehicle to do so depends in some measure on the rearward reaction imposed on the vehicle in order to produce travel of the wheels on the suspension. Since most suspension systems have the wheels deflecting straight upwardly, the rearward reaction is considerable.
It is thus an object of the present invention to provde a suspension system for a wheeled vehicle which accommodates extended travel of the wheels by a simple, rugged suspension system which is readily adaptable to military off-the-road vehicles due to its ruggedness and its ability to be housed within a vehicle hull of minimal dimensions.
It is yet another object of the present invention to provide such a suspension system particularly adapted to steerable front wheels which are also powered without introducing a complex, delicate suspension component and which is accordingly extremely durable and rugged while allowing ready access to the components for maintenance purposes.
It is yet another object of the present invention to provide a suspension system in which a need for a separate shock absorber is eliminated while insuring that the suspension energy absorbed is dissipated to provide adequate damping.
It is still another object of the present invention to provide a suspension system which minimizes the rearward reaction force on the vehicle in negotiating vertical obstacles.